Open circuit in the sensor signal wire, such as a broken wire or unplugged connector; Corroded, loose, or water-intruded electrical connector at the sensor or PCM; Sensor signal circuit shorted to voltage, often from chafed wiring against a 12-volt source; Failed alternative fuel tank temperature sensor with an open internal element; High resistance in the sensor ground circuit, which the PCM interprets as a high signal voltage; Faulty PCM driver or internal pull-up resistor on the signal circuit (rare but possible); Aftermarket wiring or accessory installation that disturbed the sensor circuit

DTC codes / P01xx · Fuel and air metering / P01AD

P01ADAlternative Fuel Tank Temperature Sensor Circuit High

Q: What does code P01AD mean?

Alternative Fuel Tank Temperature Sensor Circuit High. P01AD means the powertrain control module (PCM) has detected an abnormally high voltage on the signal circuit of the alternative fuel tank temperature sensor, which is used on vehicles that run on fuels such as compressed natural gas or liquefied petroleum gas. The sensor's resistance rises as fuel temperature drops, so a high-voltage signal tells the PCM the fuel is colder than it actually is, or that the circuit is open or shorted to voltage.

P01AD means the powertrain control module (PCM) has detected an abnormally high voltage on the signal circuit of the alternative fuel tank temperature sensor, which is used on vehicles that run on fuels such as compressed natural gas or liquefied petroleum gas. The sensor's resistance rises as fuel temperature drops, so a high-voltage signal tells the PCM the fuel is colder than it actually is, or that the circuit is open or shorted to voltage.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaFuel and air metering

Symptoms you may notice

Illuminated check engine light, often with no other noticeable symptoms
Rough running or poor driveability when the engine is cold because fuel temperature is misreported
Hard starting or extended crank times in cold weather
Reduced fuel economy or power derating on some alternative-fuel vehicles
Erratic fuel gauge or fuel temperature display readings on vehicles with an instrument cluster readout
Possible no-start condition if the PCM substitutes an extreme default value that prevents fuel delivery

Common causes, most likely first

Open circuit in the sensor signal wire, such as a broken wire or unplugged connector
Corroded, loose, or water-intruded electrical connector at the sensor or PCM
Sensor signal circuit shorted to voltage, often from chafed wiring against a 12-volt source
Failed alternative fuel tank temperature sensor with an open internal element
High resistance in the sensor ground circuit, which the PCM interprets as a high signal voltage
Faulty PCM driver or internal pull-up resistor on the signal circuit (rare but possible)
Aftermarket wiring or accessory installation that disturbed the sensor circuit

How to diagnose and fix it

Connect a scan tool and record the freeze-frame data and live sensor voltage to confirm the high reading matches the code
Visually inspect the sensor, its connector, and the wiring harness for damage, corrosion, or loose pins
Disconnect the sensor and measure its resistance with a multimeter, comparing the value to the manufacturer's temperature-resistance chart
Check the signal circuit for an open or short to voltage by measuring voltage at the sensor connector with the key on and the sensor unplugged
Perform a voltage drop test on the sensor ground circuit to rule out high resistance in the return path
If wiring and ground are good, substitute a known-good sensor and clear the code to see whether it returns
If the code persists with a known-good sensor and verified wiring, test the PCM signal circuit for an internal fault before replacing the module

What the high-voltage reading really means

A high signal voltage on a temperature sensor almost always points to an open circuit or a bad ground rather than a failed sensor, so resistance-test the wiring before condemning the sensor.
On many alternative-fuel vehicles the tank temperature sensor shares a ground with other sensors, and a single corroded ground point can set P01AD along with unrelated codes.
The PCM may default to a fixed fuel temperature when the signal is out of range, which can mask driveability symptoms and make the code appear intermittent.
Water intrusion into the tank sensor connector is a common cause on vehicles that operate in wet or humid environments, and the corrosion is often hidden inside the connector body.
A short to voltage on the signal wire can be caused by a chafed harness near the fuel tank or along the frame rail, so inspect the entire run, not just the sensor end.

Can I keep driving with P01AD?

The vehicle is generally safe to drive with P01AD because the PCM substitutes a default fuel temperature, but cold-start and fuel-economy problems can worsen. Avoid extended driving if you notice rough running or a no-start condition, and have the circuit inspected before the fault leaves you stranded.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.